Taeniae coli

In summary, in intact myometrium there is no clear physiological role for CICR despite the presence of RyR. This is the conclusion reached by others for a variety of smooth muscles e.g. taeniae coli (lino 1989), stomach (Guerrero et al 1994), tracheal myocytes (Fleischmann et al 1996) and portal vein (Kamishima McCarron 1996). 

Bulbring E, T omita T 1969 Effect of calcium, barium and manganese on the action of adrenaline in the smooth muscle of the guinea-pig taenia coli. Proc R Soc Lond B Biol Sci 172 121-136 Marchant JS, Taylor CW 1998 Rapid activation and partial inactivation of inositol trisphosphate receptors by inositol trisphosphate. Biochemistry 37 11524-11533 Somlyo AV, Horiuti K, Trentham DR, Kitazawa T, Somlyo AP 1992 Kinetics of Ca2+ release and contraction induced by photolysis of caged D-myo-inositol 1,4,5-trisphosphate in smooth muscle the effects of heparin, procaine, and adenine nucleotides. J Biol Chem 267 22316-22322... 

Karaki H, Ikeda M, Urakawa N. 1967. Effects of external calcium and some metabolic inhibitors on barium-induced tension changes in guinea pig taenia coli. Jpn J Pharmacol 17 603-612. 

Little calorimetric research has been done on smooth muscle. Recently, however, Lonnbro and Hellstrand (1991) showed that chemically skinned muscle from guinea pig taenia coli produced threefold more heat on activation (pCa 4.8) than at rest (pCa 9) (pCa being -log Ca2+). With stepwise increments in [Ca2+] from pCa 9 to 4.8, the energetic cost of force maintenance tended to rise at higher [Ca2+]. Even after Ca2+ activation, force still increased beyond the point at which heat dissipation reached its maximum. 

LOnnbro, P. Hellstrand, P. (1991). Heat production in chemically skinned smooth muscle of guinea-pig Taenia coli. J. Physiol. 440, 385-401. 

Furukuwa et al. (1980) studied the effects of thyrotropin-releasing hormone on the isolated small intestine and taenia coli of the guinea pig. 

Paiva et al. (1988) studied the role of sodium ions in angiotensin tachyphylaxis in the guinea-pig ileum and taenia coli. 

Feniuk W, Dimech J, Humphrey PPA (1993) Characterization of somatostatin receptors in guinea-pig isolated ileum, vas deferens and right atrium. BrJ Pharmacol 110 1156-1164 Furukuwa K, Nomoto T, Tonoue T (1980) Effects of thyrotropinreleasing hormone (TRH) on the isolated small intestine and taenia coli of the guinea pig. Eur J Pharmacol 64 2179-287... 

Rabbit vas deferens Rat mesentery Guinea-pig taenia coli Rat bladder... 

In order to assess the selectivity of PPADS for different P2-purinoceptor subtypes, its effects on the relaxant responses to adenine nucleotides were examined in the rat duodenum [31], rat mesenteric arterial bed [30], rabbit isolated blood vessels [29] and guinea-pig taenia coli [31], tissues that are endowed with the archetypal P2Y-purinoceptor. 

Figure 4. Schild plots for the antagonism by PPADS in the carbachol-contracted guinea-pig taenia coli using a, P-methylene ATP (a,P-mATP) and 2-methylthio ATP (2-MeSATP) as agonists. Lines, which connect the mean log (DR - 1) values at the respective PPADS concentration, are drawn to highlight the biphasic nature of the Schild plots. The slopes of the overall regression lines (not shown) were 1.46 for a,p-mATP and 0.58 for 2-MeSATP. These values were significantly different from unity.

Relaxant responses to electrical field stimulation (0.5 - 16 Hz) in guinea-pig taenia coli were inhibited by PPADS at the same concentration-range as were the responses to exogenous ATP and 2-methylthio ATP (Figure 4) [31], In the presence of 100 pM PPADS, these neurogenic relaxations were (compared to controls) 10% (0.5 Hz), 6% (2 Hz), 5% (8 Hz) and 4% (16 Hz). This supports the purinergic nerve hypothesis, which postulates ATP or a related compound as NANC-transmitter [2]. 

Figure 6. Residual ecto-ATPase activity in guinea-pig taenia coli using ATP (0.1 mM) as substrate in the absence and presence of PPADS [31].

Karaki H, Nakagawa H, Urakawa N. 1986. Strontium uptake during the different modes of contraction in the smooth muscle of rabbit aorta, rat aorta and guinea-pig taenia coli. Arch Int Pharmacodyn 282 93-107. 

The TM isoform content of a variety of smooth muscle tissues has been examined by one- and two-dimensional gel electrophoresis, including aorta, pulmonary artery, carotid, trachealis, esophagus, duodenum, jejenum, taenia coli, rectum, and others (Fatigati and Murphy, 1984 Yamaguchi et al., 1984 Xie et al., 1991). In all cases, two major components were observed to be present in close to equal amounts. The designation of these as a and P was made on the basis... 

Phosphorylation of MLC is generally accepted to be the primary event involved in the initiation of smooth muscle contraction (Kamm and Stull, 1985 Somlyo and Somlyo, 1994). In triton skinned taenia coli, phosphorylation and dephosphorylation of MLC preceded contraction and relaxation, respectively (Kiihn et al.,... 

A. Vanadate-Induced Contraction in Intact Taenia coli... 

Because earlier studies in this and other laboratories showed that inhibitors of tyrosine kinase activity suppressed contraction of smooth muscle (Section II), we suspected that vanadate-induced contraction might be due to its efficacy as an inhibitor of tyrosine phosphatase activity. Our experiments showed that treatment of taenia coli with 1.5 mM vanadate induced a tonic contraction that was associated with enhanced tyrosine phosphorylation of at least three substrates (M 85,000, 116,000, and 205,000 Figs. 2A and 2B). Maximal force attained in response to vanadate was about one-fourth to one-third of the maximal force attained during the phasic contraction elicited by stimu-... 

In this section we review data showing that activation of smooth muscle preparations induces tyrosine phosphorylation of several substrates. As shown in Fig. 7, a similar set of substrates (M, 42,000-205,000) are tyrosine phosphorylated during (1) activation of muscarinic receptors in intact taenia coli, (2) vanadate-induced contraction of the same preparation, (3) activation of aj-adrenergic receptors in VSMC cultured from canine femoral artery, and (4) Ca +-activated contraction of permeabilized ileal longitudinal smooth muscle. It is likely that one or more of these substrates... 

FIGU R E 7 A similar set of substrates is tyrosine phosphorylated during activation of either intact taenia coli, cultured VSMC, or staphylococcal a-toxin-permeabilized deal longitudinal smooth muscle. In these experiments, tyrosine.-phosphorylated substrates were detected by immunoblotting with antiphosphotyrosine antibodies and enhanced chemiluminescence technology rather than the less sensitive I-labeled protein A technology used in Fig. 2. Stimulation of guinea pig taenia coli with either 10 jcM carbachol (Carb) or 1.5 mM vanadate (Van) resulted in pronounced tyrosine phosphorylation of at least nine substrates with apparent masses of 42-45, 50, 70, 80-85, 95,100, 110, 116, and 205 kDa. In like fashion, stimulation of canine femoral VSMC with 100 jjlM phenylephrine (PE) resulted in enhanced tyrosine phosphorylation of a similar set of substrates (however, note that qualitative differences were evident with respect to some substrates, such as the one of 205 kDa). Similarly, the same substrates appeared to be tyrosine phosphorylated when permeabilized ileal smooth muscle was contracted with Ca + (pCa 4.5). From Di Salvo et al. (1994), Fig. 5, p. 1438. 

FIGURES Force responses (middle) to length ramps (upper) in a skinned guinea pig taenia coli fiber. Lower panel shows plots of force versus length during ramps. Stiffness increases with rate of length change. From Arheden and Hellstrand (1991). 

---